Polyphase electron-tube generator



Feb. 4, 1930. R. D. DUNCAN, JR

POLY PHASE ELECTRON TUBE GENERATOR v Filed June ,28, 1927 INVENTOR.

illllll Patented Feb. 4, 1930 UNITED STATES PATENT orricr.

ROBERT D. DUNCAN, JR., EAST ORANGE, NEW JERSEY, ASSIGNOR, BY MESNE AS- SIGNMENTS, TO FEDERAL TELEGRAPH COMPANY, A CORPORATION OF CALIFORNIA I POLYPHASE ELECTRON-TUBE GENERATOR Application filed June 28,

' .rent into polyphase high frequency current without the employment of a large amount of apparatus or complex electrical circuits.- v Other and further objects of my invention will be understood from the specification hereinafter following by reference to the accompanying drawing which diagrammatically illustrates the circuit arrangement of'my invention; ,Hitherto in the art of generating polyphase high frequency current where the three electrode electron tube is employed, it has been necessary to generate first single phase current, then by means of special circuits in combination with single phase electron tube amplifiers to convert from single phase into polyphase current. A disadvantage of such arrangement is the more of less complex nature of; the circuits involved. and the relatively large number of electronjtubes required. V l My invention contemplates a form of multi-electrode electron tube and associated I circuits by means'of which polyphase and in particular three phase alternating current of any desired frequency may be generated directly without the useof a source of single phase .current and intermediate phase displacing circuits. 5 In my co-pending application S. N. 88,279, filed Feb. 15, 1926, there has been disclosed a type'of multi-element electron tube within which a rotating electric field is established for the purpose of converting from single phase to polyphase alternating current. In the present invention a similar type of electron tube is employed utilizing the feature of a rotating electric field or electron stream 7 which by means of the tube and circuit arrangement employed converts directly from 1927. Serial No. 202,081.

direct current to polyphase alternating current. Referring to the drawing, I have shown a tube and circuit for generating three phase alternating current, the numeral 1 represents a filament electrode here shown in the form of a straight wire which may be of material commonly employed for this purpose. Surrounding filament 1 and concentric therewith are three grid electrodes 2, 3, and 4, which are angularly displaced around the filamentby 120. Grids 2, 3 and 4 are shown to be of lattice construction and are separated from oneanother by spaces 5, 6 and 7. Surrounding both filament and grid electrodes are three plate electrodes 8, 9, 10 which are also concentric with the filament and are angularly displaced around the filament by 120. Both grid and plate electrodes are shown for convenience, to be in the form of arcuate segments. This however, need not necessarily be the case, as they may take any desirable form as long as they are symmetrically positioned around the filament and displaced by appropriate angles. Filament 1, grids 2, 3, 4, plates 8, 9, 10 are appropriately mounted and contained within a hermeticallysealed vessel 11, which is assumed to be evacuated by any of the wellknown processes, in order toobtain an electron discharge from'filament 1. Connections 12 and 13 are brought out from within vessel 11 from the two ends of filament 1 and connectwith battery 14, the negative terminal of which is grounded at 15. Battery'14serves to render the filament incandescent for the production of electrons. Additional connec tions 16, 17, 18 respectively from grids 2, 3, 4, are brought out of vessel 11. A third set of leads 19, 20, 21 connecting respectively with plates 8, 9, 10 are brought out'from vessel 11. Lead 19 connects through condenser 22 to circuit 23, composed of inductances 24, 25 and variable capacity 26. In a similar manner, leads 20 and 21 respectively connect through condensers 27 and 28 to circuits 29 and 30, composed of inductances 31, 32 and 33, 34 and capacities 35 and 36. Gircuits 23,29 and 30 are grounded at 15. Inductively coupled to'inductances 24, 31 and 33 are respectively inductances 37, 38, 39

which are themselves connected in closed delta. From the apeXes of the delta extend leads 16, 17 and 18 connected respectively 7 with grids 2, 3, and 4. Connected in star to the apeXes of delta connected inductances 37, 38, 39 are grid leak resistances 50, 51, 52, the

common point of which is grounded through rent generator, the negative terminal of which is grounded at 15. The positive terminal connects to plate leads 19, 20, 21 through choke coils 61. It will be noted that circuits 23, 29, 30 are interconnected through ground connection in Y with respect to filament 1 also grounded at 15, while the circuit composed of inductances 37, 38, 39 is connected in closed delta. The ground 15 serves as a common point of connection.

The method offunctioning of the arrangement of the drawing is as follows: The lilament 1 is rendered incandescent by passage of current from battery 14. I An electron field is therefore established in the evacuated space surrounding the filament. When the plates 8, 9, 10 are charged positively by closing the circuit of voltage source 60, a stream of electrons is drawn to each of plates 8, 9, 10 in the manner usual to any type of three electrode tube. At the same time the closing of the plate circuit will establish transient oscillations in each of circuits 23,29, and

the frequency. of these transients will correspond to the natural-frequency of their circuits, here assumed to be substantially the same. By virtue of the coupling between inductances 24-37, 31-38 and 3339, transient voltages are established in grid inductances 37, 38, 39. Now it is observed that in ductances 37, 38, 39 are connected in closed delta, viz, from a closed. circuit and in accordance with Kirchoifs law the vector sum of the voltages induced in the circuit must equal zero. Imposing the restriction that the transient voltageinduced in inductances 37, 38, 39 be substantially equal, and in view of Kirchoifslaw notedabove, it is evident from the fundamental theory of three phase alternating currents that the equal transient voltages set up in 37, 38,- 39 will diifer in phase by substantially 120 electrical degrees, and therefore because of connections 16, 17, 18 to grids 2, 3., 4 there will be initially established between these grids transient voltages cliffering in phase by 120. Focussing attention 88,279, filed Feb. 15, 1926, that a three phase electron field surrounding the filament 1 will cause the electrons in the evacuated space surrounding filament 1 to revolve around the filament and impinge cyclically upon plates 8, 9,10. Finally, fulfilling the well-known conditions for sustained oscillations which must exist between anythree electrode tube and its input and output circuits the attenuation of the transient voltages and currents tube generator is obtained. Due to the coupling between inductances 2540, 32-41, and

3442, three phase currents are established in the three phase transmission line 49.

' The circuit arrangements of my invention have been found to be efficient in operation and highly practical in view of their simplicity. The combination of the closed delta connected grid inductances and the Y connected plate circuits provides for stabilized operation of the .polyphase system at a sub-' stantially constant frequency.

l Vhile I have described my invention in one of its preferred embodiments, I desire y that it be understood that modifications may be made and that no limitations upon my invention are intended other than are imposed by the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the, United States is as follows:

1. In a system for generating polyphase high frequency current, an electron tube having a cathode and a plurality of grid and plate electrodes disposed adjacent thereto, means for heating said cathode, a closed delta circuit connecting said grid electrodes, a Y connected circuit connecting said plate electrodes, a load circuitcoupled with said Y connected circuit and coupling means between sustained or unsaid .closed delta circuit and said Y connectgrid electrodes and a plurality of plate electrodes, each of said grid .electrodes displaced with respect to each other, and each of said plate electrodes displaced 120 with respect to each other around saidcathode, a

set of inductances connected in delta and con,- nected with said grid electrodes, a separate set of inductances connected in Y and connected with said plate electrodes, a work circuit and means coupling saidY connected inductances with said work circuit and with said delta connected inductances- A system, for generating three phase high frequency current comprising an electron tube having a cathode, a plurality of grid electrodes and a plurality of plate electrodes, each of said grid electrodes displaced 120 With respect to each other, and each of said plate electrodes displaced 120 with respect to each other around said cathode, a set of inductances connected in delta and connected with said grid electrodes, a set of circuits each including a pair of inductances and a capacity, with a Y connected circuit including selected ones of said inductances and said plate electrodes, a work circuit and coupling means between the inductances of said Y connected circuit, said work circuit and said delta connected circuit.

y 4. A system for generating three phase, high frequency current comprising an electron discharge tube including a cathode and sets of independent grid and plate electrodes displaced 120 around said cathode, means for heating said cathode, independent inductance elements connected in delta, with connections from the apexes of said delta to each of said grid electrodes, a tuned circuit coupled with each of said inductance elements, a Y connected circuit including said tuned circuits, a connection between each of said tuned circuits and one of said plate electrodes and a work circuit coupled with said tuned circuits for receiving three phase high frequency oscillations developed in said aforementioned circuits.

6. Asystem for generating three phase high frequency current comprising an electron discharge tube including a cathode and sets of independent grid and plate electrodes displaced 120 around said cathode, means for heating said cathode, a plurality of inductance elements arranged in delta and connectedwith said grid electrodes, a plurality of independent tuned circuits each connected tov one of said plate electrodes, each of said tuned circuits being independently coupled with a selected one of said inductance elements for the establishment oftransient oscillations therein for setting up sustained three phase high frequency oscillations in said connected circuit.

' 7. A system for generating three phase high frequency current comprising an electron tube having a cathode and sets of independent grid and plate electrodes displaced 120 around said cathode, a set of inductances connected in delta and connected with said grid electrodes, a circuit connected with each of said plate electrodes, each of said last named circuits coupled to one of said sets of delta connected inductances, and a common Work circuit for the production of three phase high frequency current in said circuits.

In testimony whereof I aflix my signature.

ROBERT D. DUNCAN, JR. 

